Sauerkraut is pickled cabbage. It's sort of spicy like regular coleslaw, but with the briney vinegar taste you get with pickled things. Traditionally it's used to complement meats like sausage and whatnot.
I had a mind to pick up some sauerkraut at the grocery store today to go with those little microwave sausages. But all they had were these enormous two-pound jars of the stuff. I mean, they're still cheap even buying the big jar, but I ask you, what am I supposed to do with two pounds of sauerkraut, hmm? It's pickled, so it's not going to go bad, but even so--that's overkill, that is. Come on.
Anyway, cabbage is a good source of vitamins, I guess.